WO2005015271A2

WO2005015271A2 - Security element with a thin layered element

Info

Publication number: WO2005015271A2
Application number: PCT/EP2004/008912
Authority: WO
Inventors: Manfred Heim; Ralf Liebler; Markus Krombholz
Original assignee: Giesecke & Devrient Gmbh
Priority date: 2003-08-12
Filing date: 2004-08-09
Publication date: 2005-02-17
Also published as: CN1852808A; DE502004002703D1; US20070190297A1; WO2005015271A3; RU2344048C2; DE10337331A1; EP1658179A2; EP1658179B1; CN100415537C; US7923097B2; RU2006107440A

Abstract

The invention relates to a security element for security documents, documents of value and similar, comprising a thin-layered element (12) having a variable coloration effect, consisting of a reflective layer (14), an absorbent layer (18) and a spacer layer (16) arranged between the reflective layer (14) and the absorbent layer (18). According to the invention, the spacer layer (16) is formed by a compression layer with dispersion particles (20) having a monomodal or oligomodal size distribution.

Description

Security element with thin-film element

The invention relates to a security element for security papers, documents of value and the like with a thin-layer element with a color-shift effect, which has a reflection layer, an absorber layer and a spacer layer arranged between the reflection layer and the absorber layer. The invention also relates to a security paper, a value document, a method for producing such a security element and a printing ink with optically variable color pigments and a manufacturing method for such a printing ink.

Valuable documents, such as banknotes, shares, bonds, certificates, vouchers, checks, high-quality admission tickets, but also other documents that are susceptible to counterfeiting, such as passports or other identification documents, are generally provided with various security features to increase counterfeit security. The security feature can be embodied, for example, in the form of a security thread embedded in a banknote, an applied security strip or a self-supporting transfer element, such as a patch or a label, which is applied to a document of value after its production.

It is known to use security features with multilayer thin-film elements whose color impression for the viewer changes with the viewing angle, for example from green to blue, from blue to magenta or from magenta to green. The color effect is based on interference effects due to multiple reflections in the different sub-layers of the thin-film element and is described in detail, for example, in EP 0 395 410 B1. Such color changes when a security feature is tilted are referred to below as a color shift effect or color shift effect. As the layer mainly responsible for the color effect, the thin-layer elements contain an ultra-thin (usually about 100 to 500 nm thick) dielectric layer, which is typically arranged between an absorber layer and a reflection layer. The thin dielectric layers are produced using a complex vacuum evaporation process. In particular with the large-area coatings required in the area of security papers and banknotes, the requirements for precision are extremely high, so that such coatings can only be carried out in a few locations worldwide.

Proceeding from this, the object of the invention is to provide a generic security element which is easier and cheaper to manufacture than the prior art.

This object is achieved by the security element with the features of the main claim. A security paper for the production of security documents, a value document with such a security element and a manufacturing method for such a security element are the subject of the independent claims. In a further aspect, the invention contains a printing ink with optically variable color pigments and a production method for such a printing ink. Developments of the invention are the subject of the dependent claims.

The security element according to the invention is based on the prior art in that the spacer layer is formed by a printing layer with dispersion particles with a monomodal or oligomodal size distribution. Since there are only dispersion particles with a certain size (monomodal distribution) or with a few, differentiated sizes (oligomodal distribution) in the print layer, a very high one can be found Layer thickness constancy of the spacer layer can be achieved, as will be explained in more detail below.

According to a preferred embodiment of the invention, the printing layer contains a main species of essentially spherical, monodisperse dispersion particles, the diameter of which determines the thickness of the spacing layer. In the context of the present invention, particles are referred to as monodisperse if they are very narrowly distributed, preferably when σ _m / d _m <20%, particularly preferably <5%, where d _{m is} the mean and σ _{m represents} the standard deviation of the size distribution. Clearly speaking, the monodisperse dispersion particles of the printing ink all have essentially the same diameter dm-monodisperse particles also have a monomodal size distribution, since the mean diameter d _{m represents} the only mode of size distribution.

The dispersion particles of the main species preferably have a diameter dm which is between approximately 100 nm and approximately 1500 nm, preferably between approximately 200 nm and approximately 1000 nm, particularly preferably between approximately 200 nm and 500 nm. In order to obtain a desired color effect, dispersion particles with a diameter d _{m are} selected taking into account the refractive index n of the material, so that the required optical thickness n * d _{m of} the spacer layer is achieved. With the specified diameter range of the dispersion particles, practically any desired color shift effect can be achieved by means of the printed spacer layer.

The printing layer expediently comprises a monolayer or submonolayer of the dispersion particles of the main species. Because of the uniform size the dispersion particle also has a very uniform thickness of the monolayer or submonolayer. This measure also ensures a uniform layer thickness of the printing layer in a larger surface area, in particular over the web width of a roll.

According to an advantageous embodiment of the invention, the dispersion particles are designed such that they melt in a process following the printing process. For this purpose, the dispersion particles of the main species preferably have a melting temperature in the range from 50 ° C. to 250 ° C., particularly preferably in the range from 80 ° C. to 120 ° C.

A possibly uneven surface of the print layer can be leveled by the melting. At the same time, the adhesion of the dispersion particles to one another and the adhesion of the particles to the underlying layer is improved. The color purity of the thin-film element can be significantly improved by leveling the print layer.

The dispersion particles of the main species can be formed, for example, from polystyrene, styrene-acrylic-nitrile copolymers (SAN), aromatic polyesters or polyamides.

According to another advantageous embodiment of the invention, the dispersion particles of the main species have a core-shell structure with an infusible or high-melting core and a slightly film-forming shell. With such a structure, the core of the dispersion particles remains stable during a temperature step, while the shells of the dispersion particles melt and form an ideally continuous film. This film achieves a very good leveling of the print layer. In addition, the adhesion of the print layer to the underlying layer and the adhesion of the dispersion particles to each other greatly increased.

In advantageous configurations, the core of the dispersion particles is formed from a hard polymer such as polystyrene, PMMA, styrene-acrylic-nitrile copolymers (SAN), aromatic polyesters or polyamides and the shell from PMMA, polybutadiene or polyisoprene.

According to a further preferred embodiment, in addition to the dispersion particles of the main species, the printing layer also contains dispersion particles with a smaller size, which are arranged in spaces between the substantially spherical dispersion particles of the main species. In this case, the size distribution of the dispersion particles is oligomodal, since in addition to the main species with a diameter d _{m, there is} at least one further species with a diameter d _z <d _m . If the size of the other species is significantly smaller than the diameter of the main species, the dispersion particles of the additional species lead to a smoothing and leveling of the print layer. The diameter of the smaller species is preferably less than 0.5 * d _m , particularly preferably less than 0.25 * d _m . It is understood that the size distribution of the smaller dispersion particles need not be as narrow as that of the main species, since they do not determine the thickness of the spacer layer.

In an expedient design, the dispersion particles of smaller size have such a low melting temperature that they melt and film when the printing layer dries. As described above, this results in a leveling of the printing layer and an improved adhesion of the dispersion particles to one another and to the layer underneath. Optionally, leveling and / or filming additives, such as PVA or polysorbate 20, can also be used to optimize film formation and leveling of the surface.

In advantageous configurations, the reflection layer is formed by an opaque reflector layer, in particular made of a metal, such as aluminum, silver, nickel, copper, iron, chromium or gold.

The security element can also be designed as a semi-transparent color-shift security element. In this case, an absorber layer, a semi-transparent metal layer or a transparent reflection layer, whose refractive index is different from that of the printing layer, is used as the reflection layer instead of an opaque reflection layer. Basically, almost all of the vaporized, transparent compounds can be used as transparent reflection layers, in particular also higher refractive index coating materials such as Zr0 ₂ , ZnS, ΗO2 and indium tin oxides (ITO). The layer thickness of the transparent reflection layer is preferably in the range from 30 nm to 300 nm, particularly preferably 50 nm to 60 nm.

Typically, metal layers made of materials such as chromium, iron, gold, copper, aluminum or titanium are used as absorber layers in a thickness of preferably 4 nm to 20 nm. Compounds such as nickel-chromium-iron or more rare metals such as Vanadium, palladium or molybdenum can be used. Other suitable materials are, for example, nickel, cobalt, tungsten, niobium, aluminum, metal compounds, such as metal fluorides, oxides, sulfides, nitrides, carbides, phosphides, selenides, silicides and compounds thereof, but also carbon, germanium, Cermet, iron oxide and the like. The absorber and reflection layers are preferably vapor-deposited using the vacuum evaporation method.

A wide variety of vapor deposition processes are suitable for producing the layers. One methodical group is physical vapor deposition (PVD) with boat vapor deposition, vapor deposition by resistance heating, vapor deposition by induction heating or electron beam vapor deposition, sputtering (DC or AC) and arc vapor deposition. On the other hand, the evaporation can also be carried out as Chemical Vapor Deposition (CVD), e.g. Sputtering in reactive plasma or any other plasma-assisted vapor deposition. In principle, there is also the possibility of printing dielectric layers.

If dispersion particles with a different refractive index are available, the color shift security element can also be designed in such a way that the printing layer comprises two or more partial layers, each of which essentially contains spherical, monodisperse dispersion particles with a different refractive index. The partial layers can be separated by a semitransparent metal layer or, alternatively, they are arranged directly one above the other without the semitransparent metal layers lying in between. In this case there is an almost fully transparent security element with a different color impression from different viewing angles. Such a security element best unfolds its optical effect against a dark background.

If a semitransparent metal layer is applied between the individual sub-layers, a security element is obtained which, with a suitably selected transmission of the semitransparent layers, clearly noticeable color shift effect even without an absorbent background.

According to an advantageous development of the invention, the thin-film element has a second absorber layer on the side of the reflective layer facing away from the spacer layer and a second spacer layer arranged between the second absorber layer and the reflective layer, so that a thin-film element with color-shift effects visible from both sides is produced. The second spacing layer is formed by a second printing layer with dispersion particles with a monomodal or oligomodal size distribution. The second printing layer preferably contains a main species of essentially spherical, monodisperse dispersion particles, as described above in connection with the first printing layer. Such symmetrically designed security elements can be used for security papers or value documents that have a window area or a hole. The security element is attached over the window area or hole so that it is visible from both sides.

The first and second printing layers each advantageously contain a main species with a different diameter and / or different refractive index, so that a different color shift effect can be seen on both sides of the security element.

A matrix filling of polymer material is expediently arranged in the spaces between the dispersion particles, which levels out the printing layer and ensures good adhesion of the dispersion particles to one another and to the layer underneath. Such a matrix filling can be done in one temperature step, for example by filming the shells of Core-shell dispersion particles or by filming an additional species of dispersion particles.

In an advantageous development of the invention, the thin-film element is provided with a flat diffraction structure in order to form a color shift hologram. In a variant, the absorber layer, the spacer layer and the reflector layer are arranged in this order on a support with the flat diffraction structure. In another variant, the order of the layers is reversed, so that the reflector layer, the spacer layer and the absorber layer are arranged on the carrier in this order.

The carrier can be formed, for example, by an embossing lacquer layer provided with a diffraction structure on a plastic film, which forms part of the finished security element. The diffraction structure of the embossing lacquer layer continues vertically upwards when the further layers are applied in it. The layers can also be produced on an intermediate carrier which is removed when the security element is finished or at the latest when the security element is applied or introduced into an object. The absorber layer of such a color shift hologram typically has a transmission between 25% and 75%. The thin-layer structure of the security elements according to the invention is preferably applied to a substrate. The substrate is preferably a transparent plastic film, e.g. Polyester.

The security elements described above can be, for example, in the form of a security strip, a security thread, a security tape, a label-shaped individual element (patch) or a transfer element be designed for application to security paper, value document or the like.

The invention also includes a security paper for the production of security documents, such as banknotes, identity cards or the like, which is equipped with a security element described above. The security paper can in particular contain at least one continuous window area or a hole which is covered with the security element. In this case, it is advantageous to use a symmetrical security element, the color shift effects of which are visible from both sides.

The invention also includes a document of value equipped with a security element described above, for example a bank note. The value document can also contain a window area covered with the security element or a hole covered therewith.

The described security element, security paper or value document can be used, among other things, to secure goods of any kind.

In order to produce a security element for security papers, documents of value and the like, which contains a thin-layer element with a color-shift effect, which has a reflection layer, an absorber layer and a spacer layer arranged between the reflective layer and the absorber layer, the invention provides that the spacer layer in a printing process with a printing ink with dispersion particles is applied with monomodal or oligomodal size distribution. The spacer layer is applied in particular by means of gravure printing, flexographic printing or offset printing. A printing ink is preferably used which contains a main species of essentially spherical, monodisperse dispersion particles. The solids content of the ink and the amount transferred are expediently set during the printing process in such a way that a monolayer or submonolayer with the dispersion particles predominantly forms on the reflection layer.

The printed spacer layer is advantageously subjected to a temperature step in which at least one component of the printing ink melts. The melting component can be formed, for example, by the dispersion particles themselves, the shell of the dispersion particles or an additional dispersion particle species. The melted component films and levels the printed layer and improves the adhesion of the dispersion particles to each other and to the substrate.

If the thin-layer element has a second spacer layer and a second absorber layer on the side of the reflective layer facing away from the spacer layer, then according to the invention the second spacer layer is likewise applied in a printing process using a printing ink with dispersion particles with monomodal or oligomodal size distribution. The result is a symmetrical thin-film element with color tipping effects visible from both sides. For the second spacer layer, a printing ink is preferably used, as for the first spacer layer, which contains a main species of essentially spherical, monodisperse dispersion particles. According to a preferred further development, printing inks are used for the first and second spacer layers, each of which contains a main species with a different diameter and / or different refractive index, so that different color-shifting effects can be seen from the two sides in the thin-layer element.

The printing of the spacer layer or, in the case of a symmetrical thin-layer element, both spacer layers is particularly advantageously carried out by roll with a layer thickness that is uniform over the web width.

In a further aspect, the invention contains a printing ink with optically variable color pigments which are formed by interference layer particles.

The layer structure of the interference layer particles comprises a reflection layer, an absorber layer and a spacer layer arranged between the reflection layer and absorber layer, the spacer layer being formed by a printing layer with dispersion particles with monomodal or oligomodal size distribution. With regard to the advantageous diameter, structure, choice of material, arrangement and other properties of the dispersion particles, reference is made to the above statements in connection with the security element, which also apply to the dispersion particles of the printing ink.

In a method for producing a printing ink with optically variable color pigments, a thin-layer element with a color-shift effect is applied to a substrate by applying a reflection layer, an absorber layer and a spacer layer to the substrate, the spacer layer being used in a printing process with dispersion particles with monomodal or oligomodal Size distribution is applied, the thin layer element is detached from the substrate, the detached thin-layer element is ground to a given particle size and the particles are introduced into a binder as optically variable color pigments.

With printing inks of this type, it is advantageous if there is a dark background beneath the reflection layer, preferably black ink is printed. Interference pigments, which do not lie with the desired interference layer structure but with the black background on top when printing the printing ink, interfere far less with the color impression than pigments that come with the reflection layer on top. The latter reflect white light relatively strongly, which disturbs the desired color impression due to the interference layer structure.

In a preferred embodiment, the layer structure of the interference layer particles comprises a first absorber layer, a first spacer layer, a reflection layer, a second spacer layer and a second absorber layer, the first spacer layer being arranged between the reflection layer and the first absorber layer, and the second Spacer layer between the reflection layer and the second absorber layer is arranged. The first and second spacing layers are formed by a first and a second printing layer with dispersion particles with monomodal or oligomodal size distribution.

The first and second spacer layers of the interference layer particles each preferably contain a main species of essentially spherical, monodisperse dispersion particles, the diameters of which determine the thickness of the first and second spacer layers. Regarding the advantageous diameter, the structure, the choice of material, the arrangement and other properties of the dispersion particles, reference is made to the above statements in In connection with the security element referenced, which also apply to the dispersion particles of the printing ink.

In a method for producing a printing ink with optically variable color pigments a), a thin-layer element with a color shift effect is applied to a substrate by applying a first absorber layer, a first spacer layer, a reflection layer, a second spacer layer and a second absorber layer to the substrate in this order the first and second spacer layers are each applied in a printing process with a printing ink with dispersion particles with monomodal or oligomodal size distribution, b) the thin-film element is detached from the substrate, c) the detached thin-film element is ground to a given particle size, and d) the particles are introduced into a binder as optically variable color pigments.

For the details of the application of the spacer layers, reference is again made to the above statements in connection with the security element. The advantageous embodiments mentioned there also apply to the production of the printing ink.

It also applies to all of the exemplary embodiments according to the invention that the spacer layer is partially constructed from different dispersion particles. This means that it is possible to achieve different color shift effects at different points. For example, two or more areas with dispersion particles of different sphere sizes can be printed side by side become. It is also conceivable to overprint a full-surface spacer layer with dispersion particles of a certain size with a further spacer layer with dispersion particles of a different size, depending on the motif. In the security elements equipped in this way, the viewer can perceive different color shift effects at different points.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures. For the sake of clarity, the figures are drawn to a representation true to scale and proportion.

Show it:

1 shows a schematic illustration of a banknote with a color shift transfer element attached, according to an exemplary embodiment of the invention,

2 shows the color shift element of FIG. 1 in cross section,

3 in (a) a printing ink with monodisperse dispersion particles with a core-shell structure, and in (b) a color shift element with a spacer layer printed with the printing ink from FIG. 3 (a) according to another exemplary embodiment of the invention .

4 in (a) a printing ink which, in addition to a moon-disperse main species, also contains high-melting dispersion particles of smaller diameter, and in (b) a color shift element with an impression printed with the printing ink of FIG. 4 (a) base layer according to a further exemplary embodiment of the invention,

5 in (a) a printing ink which, in addition to a moon-disperse main species, also contains slightly film-forming dispersion particles of smaller diameter, and in (b) a color shift element with a spacer layer printed with the printing ink of FIG. 5 (a) another embodiment of the invention,

6 shows a color shift element according to a further exemplary embodiment of the invention in cross section,

7 shows a section through a banknote with a punched-out opening, which is covered by a color shift element of the type shown in FIG. 6,

8 shows a color shift hologram according to a further exemplary embodiment of the invention in cross section, and

9 shows a printing ink with optically variable color pigments according to an embodiment of the invention.

The invention will now be explained using the example of a banknote. Fig. 1 shows a schematic representation of a bank note 10 with a glued on

Color shift transfer element 12. The color shift element 12 may, as shown below, cover a window area or a hole in the banknote, or it may be attached to a closed and essentially opaque part of the banknote. In the latter case, the one with reference 1 to 5 will now be explained in more detail, the color shift element 12 has only a color shift effect visible from the front.

The layer structure of the color shift element 12 according to a first exemplary embodiment of the invention is shown schematically in cross section in FIG. 2. The color shift element 12 has a reflection layer 14 which is formed by an opaque metal layer, an absorber layer 18 and a spacer layer 16 arranged between these layers.

In the exemplary embodiment, the spacer layer 16 is printed with a printing ink with monodisperse dispersion particles 20 which have a diameter of 400 nm. After the printing ink has dried, the dispersion particles 20 form a uniform and regular structure on the reflection layer 14. The solids content of the printing ink and the transfer amount are adjusted so that essentially a monolayer of dispersion particles 20 is formed on the surface of the reflection layer 14.

Because of the uniform diameter of the monodisperse dispersion particles 20, the spacer layer 16 is very uniform

Layer thickness that essentially corresponds to the diameter of the dispersion particles 20. Defects or gaps in the ordered structure formally form a submonolayer of dispersion particles 20. However, these order errors do not lead to a deterioration in the layer thickness constancy as long as the occupancy density of the dispersion particles 20 is only large enough. It goes without saying that the diameter of the dispersion particles 20 is selected in accordance with the desired color of the color shift element 12, taking into account the refractive index of the dispersion particle material.

3 shows in (a) a printing ink 22 in which monodisperse core-shell particles 24 are dispersed in water. The core-shell particles 24 have a high-melting core 26 and a slightly film-forming shell 28. For example, the core 26 can be made of polystyrene and the shell 24 can be made of polybutyl acrylate. After the printing ink 22 has been applied to the reflection layer 14, the spacer layer 16 is dried in a subsequent process step. The shells 28 of the dispersion particles 24 melt and film into an embedding matrix 30, as shown in FIG. 3 (b). As a result, the printing layer 16 is leveled and the adhesion of the remaining cores 26 of the dispersion particles to one another and to the underlying reflection layer 14 is improved.

Another embodiment of the invention is shown in FIG. 4. The printing ink 32 of FIG. 4 (a) contains, in addition to a moon-dispersed main species 34, also high-melting dispersion particles 36 of smaller diameter. In the exemplary embodiment, the size distribution of the dispersion particles 34 and 36 is therefore bimodal. When the printing ink 32 is printed on the reflection layer 14, the smaller dispersion particles 36 fill the spaces 38 between the larger particles 34 and thus level the printing layer 16. It is understood that the size distribution of the smaller particle species 36 need not be as narrow as the distribution of the main species 34, since they are of secondary importance for the thickness of the spacer layer 16. 5 shows a further exemplary embodiment with an ink 40, in which the smaller dispersion particles 42, in contrast to the ink 32 just described, are slightly film-forming. After the application of the printing ink 40 to the reflection layer 14, the dispersion particles 42 are fused into a film 44 in a temperature step. As described in connection with FIG. 3, the embedding film 44 results in a leveling of the printing layer 16 and an improved adhesion of the main species 34.

A security element with a symmetrical layer structure, in which a color shift effect is visible from both sides, is illustrated in FIG. 6. The thin-layer element 50 shown there contains a first absorber layer 52, a first spacer layer 54, an opaque reflector layer 56, a second spacer layer 58 and a second absorber layer 60. As described above, both spacer layers 54 and 58 are mono-modal or by a printing layer oligomodal sized dispersion particles formed.

In the exemplary embodiment, the first spacer layer 54 is printed with a printing ink with monodisperse dispersion particles 62 with a diameter of 400 nm, the second spacer layer 58 with a printing ink with monodisperse dispersion particles 64 with a diameter of 300 nm. Corresponding to the different sizes of the dispersion particles 62, 64 occur the front and back of the thin-film element 50 different color shift effects. It goes without saying that dispersion particles with a core-shell structure or printing inks with additional dispersion particles of smaller diameter, as shown in FIGS. 3 to 5, can also be used for the symmetrical security element. An application of the symmetrical thin-film element 50 is shown in FIG. 7, which shows a bank note 70 with a continuous punched opening 72. The opening 72 on the front of the banknote 70 is completely covered by the thin-film element 50 of FIG. 6. Because of the opaque reflection layer 56, viewed from the front of the banknote 70, only the color-shift effect determined by the upper spacer layer 54 with its 300 nm diameter dispersion particles is visible.

If the banknote 70 is viewed from the rear, the opening 72 shows the rear of the thin-film element 50, and thus only the second color shift effect determined by the lower spacer layer 58 and the 220 nm dispersion particles. The color shift effect, which is different from both sides, is easy to check even for laypeople, but is difficult to imitate and thus considerably increases the security of the banknote provided with the security element 50.

The security element 80 of the exemplary embodiment shown in FIG. 8 represents a so-called color shift hologram. The security element 80 contains a thin-layer element 82 with a color shift effect, which is additionally provided with a flat diffraction structure 84. For this purpose, an embossing lacquer layer 88 is applied to a carrier film 86, into which a diffraction structure 84 is embossed. A semitransparent absorber layer 90 with a transmission between 25% and 75%, in the exemplary embodiment of about 50%, is vapor-deposited on the embossing lacquer layer 88.

A spacer layer 92 is applied to the absorber layer 90 and is formed by a printing layer described above with dispersion particles of monomodal or oligomodal size distribution. 8, for the sake of simplicity, only the case of a monodisperse species illustrated by dispersion particles 94, it goes without saying that all the other dispersion particles described can also be used.

The spacer layer 92 is coated with a reflector layer 96, in the exemplary embodiment made of aluminum. When the absorber layer 90, the spacer layer 92 and the reflector layer 96 are applied, the flat diffraction structure 84 of the embossing lacquer layer 88 continues upward into the applied layers, so that when the color shift hologram 80 is finished, all sub-layers have a diffraction structure. The area of application of such color shift holograms 80, which are produced by printing technology, is just as broad and versatile as that of conventional diffraction holograms.

The symmetrical thin-film elements 50 described in connection with FIG. 6 can be used to produce a printing ink with optically variable color pigments. Such a printing ink is shown schematically in FIG. 9. To produce the printing ink 100, a thin-layer element 50 with a color-shift effect, as described in detail in connection with FIG. 6, is applied to a substrate. The thin film element 50 is then detached from the substrate and the detached thin film element is ground to a given particle size. The particles are then introduced into a binder 100 as optically variable color pigments 102. In this way, optically variable color pigments for printing inks can be produced simply and inexpensively.

Claims

Patent claims

1. Security element for security papers, documents of value and the like with a thin-layer element (12) with color-shift effect, which has a reflection layer (14), an absorber layer (18) and a spacer layer (16) arranged between the reflection layer (14) and the absorber layer (18) ), characterized in that the spacer layer (16) is formed by a printing layer with dispersion particles (20) with monomodal or oligomodal size distribution.

2. Security element according to claim 1, characterized in that the printing layer contains a main species of substantially spherical, monodisperse dispersion particles (20), the diameter of which determines the thickness of the spacer layer (16).

3. Security element according to claim 2, characterized in that the dispersion particles (20) of the main species have a diameter which is between approximately 100 nm and approximately 1500 nm, preferably between approximately 200 nm and approximately 500 nm.

4. Security element according to claim 2 or 3, characterized in that the printing layer comprises a monolayer or submonolayer of the dispersion particles (20) of the main species.

5. Security element according to at least one of claims 2 to 4, characterized in that the dispersion particles (20) of the main species have a melting temperature in the range from 50 ° C to 250 ° C.

6. Security element according to at least one of claims 2 to 5, characterized in that the dispersion particles (20) of the main species from polystyrene, styrene-acrylic-nitrile copolymers (SAN), aromatic polyesters or polyamides are formed.

7. Security element according to at least one of claims 2 to 4, characterized in that the dispersion particles (24) of the main species have a core-shell structure with a high-melting core (26) and a slightly film-forming shell (28).

8. Security element according to claim 7, characterized in that the core (26) of the dispersion particles made of a hard polymer such as polystyrene, PMMA, styrene-acrylic-nitrile copolymers (SAN) or aromatic polyester, and the shell (28) made of PMMA, polybutadiene or polyisoprene is formed.

9. Security element according to at least one of claims 2 to 8, characterized in that the printing layer in addition to the dispersion particles (34) of the main species also contains dispersion particles (36) with a smaller size, which in the spaces (38) of the dispersion particles (34) Main species are arranged.

10. Security element according to at least one of claims 1 to 9, characterized in that the reflection layer (14) is opaque.

11. Security element according to at least one of claims 1 to 10, characterized in that the reflection layer (14) is formed by a semitransparent metal layer.

12. Security element according to at least one of claims 1 to 10, characterized in that the reflection layer (14) is formed by a transparent reflection layer which has a different refractive index from the printing layer (16).

13. Security element according to at least one of claims 1 to 12, characterized in that the printing layer comprises two or more partial layers, each of which contains essentially spherical, monodisperse dispersion particles with a different refractive index.

14. Security element according to claim 13, characterized in that at least two partial layers are separated by a semitransparent metal layer.

15. Security element according to claim 13 or 14, characterized in that at least two partial layers are arranged directly one above the other.

16. Security element according to at least one of claims 1 to 15, characterized in that the thin-film element (50) on the side of the reflection layer (56) facing away from the spacer layer (52) has a second absorber layer (60) and one between the second absorber layer (60 ) and the reflection layer (56) arranged second spacer layer (58), so that a thin-layer element (50) with color-shift effects visible from both sides is created, the second spacer layer (58) by a second print layer with dispersion particles (64) with monomodal or oligomodal Size distribution is formed.

17. Security element according to claim 16, characterized in that the second printing layer contains a main species of substantially spherical, monodisperse dispersion particles (64), as described in at least one of claims 3 to 9.

18. Security element according to claim 17, characterized in that the first and second printing layers (54, 58) each contain a main species (62, 64) with a different diameter and / or different refractive index, so that from the two sides of the security element ( 50) different color shift effects can be seen.

19. Security element according to at least one of claims 1 to 18, characterized in that a matrix filling (30; 44) made of polymer material is arranged in the spaces between the dispersion particles.

20. Security element according to at least one of claims 1 to 19, characterized in that the thin-film element (80) is provided with a flat diffraction structure (84).

21. Security element according to claim 20, characterized in that the absorber layer (90), the spacer layer (92) and the reflection layer (96) are arranged in this order on a carrier (86, 88) with the flat diffraction structure (84).

22. Security element according to claim 20, characterized in that the reflection layer, the spacer layer and the absorber layer are arranged in this order on a support with the flat diffraction structure.

23. Security element according to at least one of claims 20 to 22, characterized in that the absorber layer (90) has a transmission between 25% and 75%.

24. Security element according to at least one of claims 20 to 23, characterized in that the flat diffraction structure is formed by an embossed structure (86, 88).

25. Security element according to at least one of claims 1 to 24, characterized in that the security element (12; 50; 80) comprises a security strip, a security thread, a security tape, a patch or a transfer element for application to security paper, value document and the like forms.

26. Security paper for the production of security documents, such as banknotes, identity cards or the like, which is equipped with a security element (12; 50; 80) according to at least one of Claims 1 to 25.

27. Security paper according to at least one of claims 16 to 18 and according to claim 26, with at least one window area or hole covered with the security element.

28. document of value, such as bank note, identity card or the like, which is equipped with a security element (12; 50; 80) according to at least one of claims 1 to 25.

29. Value document (70) according to at least one of claims 16 to 18 and according to claim 27, with at least one window area or hole (72) covered with the security element (50).

30. Use of a security element according to at least one of claims 1 to 25, a security paper according to claim 26 or 27, or a value document according to claim 28 or 29 for securing goods of any kind.

31. A method for producing a security element for security papers, documents of value and the like, which contains a thin-layer element with a color-shift effect, which has a reflection layer, an absorber layer and a spacer layer arranged between the reflective layer and absorber layer, characterized in that the spacer layer in a printing process with a printing ink Dispersion particles with monomodal or oligomodal size distribution is applied.

32. The method according to claim 31, characterized in that the spacer layer is applied by means of gravure printing, flexographic printing or offset printing.

33. The method according to claim 31 or 32, characterized in that a printing ink is used which contains a main species of substantially spherical, monodisperse dispersion particles.

34. The method according to at least one of claims 31 to 33, characterized in that the solids content of the ink and the amount of transfer during the printing process are set so that the reflection layer predominantly forms a monolayer or submonolayer with the dispersion particles.

35. The method according to at least one of claims 31 to 34, characterized in that the printed spacer layer is subjected to a temperature step in which at least one component of the printing ink melts.

36. The method according to claim 35, characterized in that the printing ink contains dispersion particles which melt during the temperature step.

37. The method according to claim 35, characterized in that the printing ink has dispersion particles with a core-shell structure with a high-melting core and a slightly film-forming shell, the shells of the dispersion particles melting and filming in the temperature step.

38. The method according to claim 35, characterized in that the printing ink in addition to a main species of dispersion particles, the diameter of which determines the thickness of the spacer layer, contains dispersion particles of smaller size which melt and film during the temperature step.

39. The method according to at least one of claims 31 to 38, characterized in that the absorber layer, the spacer layer and the reflection layer are applied in this order to a support with a flat diffraction structure.

40. The method according to at least one of claims 31 to 38, characterized in that the reflection layer, the spacer layer and the absorber layer are applied in this order on a support with the flat diffraction structure.

41. The method according to claim 39 or 40, characterized in that the absorber layer is evaporated onto the carrier or the spacer layer.

42. The method according to at least one of claims 31 to 38, characterized in that the thin-layer element has a second spacer layer and a second absorber layer on the side of the reflective layer facing away from the spacer layer, the second spacer layer also having a printing ink with a printing ink Dispersion particles with a monomodal or oligomodal size distribution are applied, so that a thin-layer element with color tipping effects visible from both sides is created.

43. The method according to claim 42, characterized in that a printing ink is used for the second spacer layer, which contains a main species of substantially spherical, monodisperse dispersion particles.

44. The method according to claim 42 or 43, characterized in that printing inks are used for the first and second spacer layers, each containing a main species with a different diameter and / or different refractive index, so that different color shift effects can be seen from the two sides in the thin-film element ,

45. The method according to at least one of claims 31 to 44, characterized in that the printing of the spacer layer (s) from roll is carried out with a uniform layer thickness over the web width.

46. Printing ink (100) with optically variable color pigments, which are formed by interference layer particles (102), the layer structure of which has a reflection layer, an absorber layer and a spacer layer arranged between the reflection layer and absorber layer, the spacer layer also having dispersion particles in a printing process monomodal or oligomodal size distribution is formed, or the layer structure of which comprises a first absorber layer (52), a first spacer layer (54), a reflection layer (56), a second spacer layer (58) and a second absorber layer (60), the first spacer layer ( 54) is arranged between the reflection layer (56) and the first absorber layer (52), the second spacer layer (58) is arranged between the reflection layer (56) and the second absorber layer (60), and wherein the first and second spacer layers (54, 58) by means of a first or second printing layer with dispersion particles ( 62, 64) with a monomodal or oligomodal size distribution.

47. Printing ink (100) according to claim 46, characterized in that the first and second printing layers each contain a main species of essentially spherical, monodisperse dispersion particles (62, 64), the diameter of which corresponds to the thickness of the first and second spacing layers (54, 58 ) determine.

48. Printing ink (100) according to claim 47, characterized in that the dispersion particles (62, 64) of the main species of the first and / or second Print layer have a diameter that is between about 100 nm and about 1500 nm, preferably between about 200 nm and about 500 nm.

49. Printing ink (100) according to at least one of claims 46 to 48, characterized in that the first and / or second printing layer each comprise a monolayer or submonolayer of the dispersion particles (62, 64) of the main species.

50. Printing ink (100) according to at least one of claims 46 to 49, characterized in that the dispersion particles (62, 64) of the main species of the first and / or second printing layer have a melting temperature in the range from 50 ° C to 250 ° C ,

51. Printing ink (100) according to at least one of claims 46 to 50, characterized in that the dispersion particles (62, 64) of the main species of the first and / or second printing layer made of polystyrene, styrene-acrylic-nitrile copolymers (SAN) , aromatic polyesters or polyamides are formed.

52. Printing ink (100) according to at least one of claims 46 to 49, characterized in that the dispersion particles of the main species of the first and / or second printing layer have a core-shell structure with a high-melting core and a slightly film-forming shell.

53. Printing ink (100) according to claim 52, characterized in that the core of the dispersion particles made of a hard polymer, such as polystyrene, PMMA, styrene-acrylic-nitrile copolymers (SAN) or aromatic polyester, and the shell made of PMMA, polybutadiene or polyisoprene is formed.

54. Printing ink (100) according to at least one of claims 46 to 49, characterized in that the first and / or second printing layer contains, in addition to the dispersion particles of the main species, also dispersion particles of smaller size which are arranged in spaces between the dispersion particles of the main species.

55. Method for producing a printing ink with optically variable color pigments, in which a thin-layer element with a color-shift effect is applied to a substrate by applying a reflection layer, an absorber layer and a spacer layer to the substrate, the spacer layer being used in a printing process with dispersion particles with monomodal or oligomodal size distribution is applied, the thin-film element is detached from the substrate, the detached thin-film element is ground to a given particle size and the particles are introduced into a binder as optically variable color pigments.

56. A process for producing a printing ink with optically variable color pigments, in which

a) a thin-film element with a color-shift effect is applied to a substrate by applying a first absorber layer, a first spacer layer, a reflection layer, a second spacer layer and a second absorber layer to the substrate in this order, the first and second spacer layers in each case using a printing process applied with a printing ink with dispersion particles with monomodal or oligomodal size distribution, b) the thin-film element is detached from the substrate, c) the detached thin-film element is ground to a given particle size, and d) the particles are introduced into a binder as optically variable color pigments.

57. The method according to claim 55 or 56, characterized in that the spacer layers are applied by means of gravure printing, flexographic printing or offset printing.

58. The method according to at least one of claims 55 to 57, characterized in that printing inks are used for the application of the spacer layers which contain a main species of substantially spherical, monodisperse dispersion particles.

59. The method according to at least one of claims 55 to 58, characterized in that the solids content of the ink and the transfer amount during the printing process are set such that a monolayer or submonolayer with the dispersion particles predominantly forms on the reflection layer.

60. The method according to at least one of claims 55 to 59, characterized in that the printing ink after application is subjected to a temperature step in which at least one component of the printing ink melts.

61. The method according to claim 60, characterized in that the printing ink contains dispersion particles which melt in the temperature step.

62. The method according to claim 60, characterized in that the printing ink has dispersion particles with a core-shell structure with a high-melting core and a slightly film-forming shell, the shells of the dispersion particles melting and filming in the temperature step.

63. The method according to claim 60, characterized in that the printing ink contains, apart from a main species of dispersion particles, the diameter of which determines the thickness of the spacer layer, dispersion particles of smaller size, which melt and film during the temperature step.